1. Field of the Invention
This invention relates to the field of small watercraft and, more particularly, to an improved air-intake system for use on a small watercraft.
2. Description of Related Art
Personal watercraft have become increasingly popular in recent years. This type of watercraft is sporting in nature; it turns swiftly, maneuvers easily, and accelerates quickly. A personal watercraft today commonly carries one rider and possibly one or two passengers.
A relatively small hull of the personal watercraft, comprising an upper deck and a lower hull, commonly defines a riders"" area above an engine compartment. An internal combustion engine frequently powers a jet propulsion unit which is positioned in a tunnel formed on the underside of the watercraft hull. The propulsion unit propels the watercraft. The engine lies within the engine compartment, below the riders"" area. An exhaust system extends between the engine and a discharge opening to expel exhaust gases either to the atmosphere or to the water. The exhaust system usually includes a water trap device that inhibits a reverse flow of water through the exhaust system from the discharge opening toward the engine.
It has become commonplace for small watercraft, such as for example, personal watercraft, to be operated in virtually any water condition, including ocean surf. Due to the design of the engine-air path, it is often possible for such small watercraft to operate for short periods of time submerged or in a substantially non-vertically oriented position. By drawing its air supply from the internal engine compartment of the small watercraft these small watercraft engines are generally able to avoid periodic interruptions in the engine-air supply occasioned by waves or other rough weather conditions submerging the external air intakes.
The present invention includes the recognition that prior layout of the engine and exhaust components in the watercraft""s engine compartment can lead to reduced engine performance under some operating conditions. One such instance is when a significant amount of water fills the engine compartment. Where the small watercraft experiences extremely rough water conditions such as ocean surf or maneuvers sharply at high speeds, a significant amount of water can quickly flow through the air ducts into the engine compartment of the watercraft. This influx of water, combined with the water already present inside the engine compartment of the watercraft, can possibly submerge or splash into the air-intake(s) of the watercraft engine. Furthermore, this trapped water will often contact various moving parts of the engine, such as a coupling between the engine""s crankshaft and the impeller shaft, which will cause further splashing of water in the engine compartment. Where water enters the air-intake(s), this water will become entrained in the fuel/air change delivered to the engine""s cylinders, which can cause the engine to lose power, sputter, stall, or, in extreme conditions, possibly damage the engine components.
While it is possible to reduce the amount of water present in the engine compartment through the use of additional bilge pumps or special hull designs, such solutions increase the number and weight of components in the small watercraft and/or may minimize the cooling-air flow through the engine compartment. In addition, it is extremely difficult to remove all water from the engine compartment. A need therefore exists for a device that reduces the possibility of a small watercraft engine intaking water in the engine compartment during rough water conditions and/or high speed maneuvers.
In addition, the exhaust system of the engine can become quite hot after extended periods of watercraft operation. The heat from the exhaust system, and in particular, from the water trap, which usually functions also as an expansion chamber or muffler, heats the surrounding air in the engine compartment. When the engine intakes the heated air, a fuel/air ratio of the produced fuel/air charge does not correspond to a desired fuel/air ratio because the heated intake air has less oxygen per given volume than normal. Engine performance consequently suffers. Accordingly, a need exists for inhibiting a flow of air within the engine compartment from the space surrounding the water trap to the engine""s induction system.
In accordance with one aspect of the present invention there is provided an improved intake system for use with a small watercraft engine located within the engine compartment of a small watercraft. The intake system comprises an air-intake box connected to the air-intake pipes of an engine located within the engine compartment of a small watercraft. The air intake box incorporates valves which serve to isolate the air intake box from splashing water in the engine compartment, thereby preventing the small watercraft from intaking a substantial amount of water. This air-intake box also permits the engine to briefly operate while the entire air-intake box is submerged.
Another aspect of the present invention involves extending a portion of the flywheel case over the flywheel and crankshaft coupling. This extension will redirect any water spray caused by the moving crankshaft coupling, thereby preventing such spray from entering the air-intake and being ingested by the engine. The extension also acts as a heat insulator, reducing the ambient heat level in the engine compartment near the air-intake system and inhibiting air flow from about this heated exhaust system with trap to the air-intake system.
Another aspect of the present invention involves the positioning of the engine in the engine compartment of the small watercraft. In one embodiment, the engine is tilted approximately 10 degrees towards the engine exhaust side of the engine, thereby raising the air-intakes of the engine above the air-exhausts. This orientation allows an air-intake box of the present invention to be attached to a standard small watercraft engine without substantially changing the air-intake/exhaust components and/or hull design.
In another aspect of the present invention is provided an improved valve design for use on the external hull of the watercraft, which prevents water from entering the engine and/or propulsion chamber through the intake-air ducts when the watercraft is inverted or in a substantially non-vertical orientation. This is accomplished by providing buoyant closures in air duct valves which are normally open but, when submerged, operate to close the air ducts and prevent water from traveling through the duct. Once the watercraft is returned to its substantially upright position, the buoyant closures reopen the air duct, returning air flow to the engine.
Further aspects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiment which follows.